Innovative technologies are needed to effectively (and efficiently) separate specific components from a variety of composite materials. For example, there is a need for toxic and/or inherently dangerous materials to be converted into commercially useful products. Also, there exists a large number of sites which are contaminated with toxic and/or radioactive waste materials. Although certain processes are known for cleaning up contaminated sites, many of them employ solvents or other chemicals which often increase the disposal problem in an attempt to reduce it.
More recently, the use of radio frequency has been employed for heating liquid wastes for both volume reduction and stabilization in solid form. This process involves the slow application of moderate levels of radio frequency (RF) power which permits melting and stimulates out gassing from liquids and solids. Another application of the use of energy for separating constituents from a base material is currently being pursued with respect to refining mineral ores.
Although the broad concept of using RF energy for separating constituents from a base material is known (e.g. mineral refinement, see U.S. Pat. Nos. 4,894,134 and 5,024,740), many problems exist which impede the cost effectiveness and general ability of RF techniques to be used in a way which makes the RF approach commercially feasible.
For example, fundamental limitations in the application of gyrotron technology has presented an impediment to implementing the power levels necessary to make the RF approach commercially feasible. The fundamental limitations in the RF approach which heretofore have impeded its application on a widespread commercial bases will now be explained.
In order for the RF approach to be commercially feasible, the process of separating constituents from a base material must be cost effective. Very often, a major determination of whether a process is cost effective involves flow rate at which the base material can be processed. It is a fundamental principal of radio frequency heating that the power absorbed by a base material is directly proportional to the volume of the material. By increasing the volume flow per unit time through a separating apparatus, the power applied must also be increased to effect the same constituent separation. Thus, the ability to deliver power to a base material has become the central focus, and critical limiting factor, regarding the rate at which constituents could be separated from base material.
In the vast majority of applications, for which constituents must be separated from a base material, a gyrotron or a gyro-frequency device is the only practical source for generating the necessary power levels. Beyond 30 GHz, the power available from classical tubes declines sharply. The gyrotron offers the possibility of high power at millimeter wave frequencies. Because of the smooth shape of the gyrotron circular wave guide, and other features of the gyrotron, it is more efficient than other microwave tubes. The power available with a gyrotron is many times greater than that available from classical tubes at the same frequency. Additionally, recent advancements in microwave tube technology have made it possible to generate power levels in the range of 200K Watt continuous wave (CW). Moreover, at least one gyrotron manufacturer is currently experimenting with a gyrotron capable of generating power in the range of one megawatt CW at 110 GH.sub.Z.
Although the generation of radio frequency power at the levels mentioned above, has potentially solved one of the primary impediments to making RF techniques for separating constituents commercially feasible, it has given rise to other problems. These will be explained in conjunction with FIG. 1.
Now referring to FIG. 1, the traditional approach when using RF energy for separating constituent materials from a base material is shown in FIG. 1. Traditionally, an RF source 10 is used (e.g. gyrotron, klystron, magnetron, etc.) for generating RF energy. This energy is conveyed through transmission line 12, window 14, transmission line 16 and into reaction chamber 18. Within reaction chamber 18 the base material 20 is metered through feed apparatus 22 and is acted upon by the RF energy within reaction chamber 18. This reaction typically involves sublimation whereby gas escapes from base material 20 and is removed from reaction chamber 18 by way of off gas pump 24.
Transmission line 12 and 16 form a conventional wave guide which functions to couple the transfer of energy from RF source 10 to reaction chamber 18. In many wave guide applications, a window is not necessary. However, in applications such as the one depicted in FIG. 1, it is critical to isolate the environment of RF energy source 10 from the environment of reaction chamber. The primary purpose for this isolation is to prevent any gases or particles released during the sublimation process to migrate into RF energy source 10. If gases or particles were permitted to enter the RF energy source, electrical arcing would occur damaging or potentially destroying the gyrotron. The traditional approach for preventing the migration of undesirable gases and particles into RF energy source 10 has been to use a window 14. Ideally, the window should be transparent (i.e. lossless) to the propagation of the electromagnetic waves while hermetically sealing reaction chamber 18 from RF energy source 10. As RF energy sources have increased in their ability to generate higher and higher power levels, various window designs have been implemented in order to withstand the heat which is generated within the window by virtue of its exposure to the electromagnetic energy. For example, U.S. Pat. No. 5,450,047 sets forth an improved wave guide window for use in high power wave guide applications. Also, an article entitled A VACUUM WINDOW OR A ONE MW CW 110 GHz GYROTRON, C. P. Moeller, J. P. Doane and M. DiMartino, General Atomics Report GA-821741 discloses a vacuum window which uses a water cooled sapphire as the dielectric.
Notwithstanding the advancements made in improving the ability of the window to be used in conjunction with higher and higher RF energy sources, the technology in generating RF energy has advanced to the point where the windows are the factor which limits the maximum power which can be developed in reaction chamber 18.
The present invention eliminates the limitations associated with the state of the art window technology (and its inability to transmit high power levels) by eliminating the requirement for a window while still hermetically sealing the RF energy source from the reaction chamber. Thus, by implementing the system of the present invention, the only factor which will limit the maximum amount of energy deliverable to a base material is the ability of the RF energy source to develop the energy and the ability of the reaction chamber to receive and focus the energy.